Thermo-Economic Evaluation of Water and Power Cogeneration Process through Thermal Desalination near a Back Pressure Combined Cycle

In this paper a comprehensive model is proposed to simulate combined cycle water and power process (CCWP) based on thermal desalination. In order to verify the performance of model، Al-Taweelah cogeneration plant in UAE is thermodynamically simulated by Thermoflex V. 19 and the results are compared with actual operating conditions. Considering shortcomings of mentioned unit، a cogeneration combined cycle is configured based on conventional power generation units in Iran. In this configuration، thermal desalination units utilize exhausting steam from a back pressure turbine as energy source. Desalination processes which are investigated in present study include Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED). Results show that increasing the backpressure from 6 to 40 bars decreases the electrical efficiency of cogeneration unit from 21 to 41%، compared to a single-purpose unit. It also leads to increment of 32 to 67% in power generation cost، but results in 23% of fuel saving. The electric power consumption of MSF unit is very high، about 3. 3 times of that of MED. This fact implies that the production cost of MSF is 12. 5% more than that of MED، which remains almost constant at 0. 88 $/m3 by changing the backpressure.